Cerro Caliche Gold Heap Leach Recovery Process Design

Source: Sonoro Gold Corp (2026)
Website: https://sonorogold.com/project/cerro-caliche

Critical Data

Overview

Sonoro Gold Corp.’s Cerro Caliche Gold Project in Sonora, Mexico, employs a proven heap leach gold recovery process designed to treat low-grade gold-silver mineralized material. The Preliminary Economic Assessment (PEA) effective December 2025 outlines a robust flowsheet centered on conventional three-stage crushing, heap leaching, and carbon-in-column (CIC) adsorption to achieve a design gold recovery of 72% and silver recovery of 26.7%. Located near the town of Magdalena, the project benefits from existing infrastructure and a favorable climate for year-round operations. The process facility is designed for a nominal throughput of 12,000 tpd in Year 1, ramping to 16,000 tpd for Years 2 through 9, processing material with average head grades of 0.36 g/t Au and 3.7 g/t Ag. The recovery method leverages the ore’s soft but abrasive nature, with crushing indices supporting a product size of P80 12.5 mm. Run-of-mine material undergoes primary jaw crushing followed by secondary and tertiary cone crushing in closed circuit with screens. The crushed product is conveyed to lined heap leach pads where a drip irrigation system distributes cyanide solution. Pregnant solution reports to two trains of five-stage CIC tanks for gold and silver loading onto activated carbon. Loaded carbon is stripped, electrowon, and refined into doré bars. Water from onsite wells and seasonal runoff supports reagent mixing and pad irrigation. This heap leach gold recovery approach optimizes capital efficiency while delivering strong metal recoveries from the deposit’s disseminated mineralization. The design incorporates dust control, solution management, and a full metallurgical laboratory for process monitoring. Cerro Caliche exemplifies modern, scalable heap leach technology applied to a bulk-tonnage gold project in a mining-friendly jurisdiction.

Key Process Stages

• Stage 1: Primary Crushing – Run-of-mine material with a top size of 600 mm is fed via a vibrating grizzly into a Sandvik CJ815 jaw crusher (1,500 mm x 1,300 mm, 200 kW). Operating at a nominal 1,111 t/h (based on 60% utilization), the primary crusher reduces ore to a product suitable for conveying to a crushed mineralized material stockpile. A belt weightometer and magnet ensure feed control and tramp metal removal.
• Stage 2: Secondary and Tertiary Crushing – Crushed material from the stockpile is reclaimed via four variable-speed vibrating pan feeders and conveyed to a secondary double-deck linear screen. Oversize feeds two Sandvik CS660C cone crushers (315 kW each, 40 mm closed side setting). Tertiary circuit uses three Sandvik CS660F cone crushers (315 kW each, 18 mm closed side setting) in closed circuit with three inclined screens. The final product achieves P80 12.5 mm and is conveyed 1.45 km to the heap leach pads via grasshoppers and a TeleStacker.
• Stage 3: Heap Leach Pad System and Solution Distribution – The lined heap leach pads are built in three phases: Phase 1A covers 353,000 m² with 60 mm HDPE LLDPE liner, Phase 1B adds 276,000 m² in Year 2, and Phase 2 adds 244,000 m² in Year 4. Crushed ore is stacked by grasshoppers and leveled by a dozer. A drip-pipe system distributes cyanide leach solution at a design irrigation flow rate of 10.0 Lph/m². Pregnant solution (approx. 19,400 t/day, AuEq grade 0.22 g/t) is collected via the lined pad system.
• Stage 4: Carbon-in-Columns (CIC) Adsorption Circuit – Pregnant solution is pumped to two parallel CIC trains, each with five upflow tanks (3.6 m diameter x 3.8 m high) configured for countercurrent contact. Activated carbon (6×12 mesh) adsorbs gold and silver as solution flows upward. Carbon is advanced periodically, and barren solution drains to the barren pond for reagent addition and recirculation. Spillage control sumps are included.
• Stage 5: Carbon Stripping, Electrowinning, and Refinery – Loaded carbon is dewatered on a 28-mesh screen and transferred to stripping vessels. Gold and silver are stripped using heated caustic-cyanide solution, then recovered in electrowinning cells. The resulting sludge is smelted in an induction furnace to produce doré bars. A reactivation kiln regenerates stripped carbon for reuse. The refinery includes a fume hood, dust collector, and bullion molds, all in a secure area.

Additional Interesting Data and Summary

Beyond the core recovery flowsheet, the Cerro Caliche Project integrates comprehensive support systems and environmental controls. The water supply relies on nearby drilled wells and seasonal rain/runoff collection, with multiple high-head pumps feeding a freshwater tank for process make-up, reagent mixing, and emergency needs. The main process plant features a fully contained reagent mixing area handling hydrated lime (bulk dry), sodium cyanide (dry super sacs), caustic soda, activated carbon, and refinery slagging reagents. A dedicated metallurgical and assay laboratory, located adjacent to the plant, provides timely monitoring of process streams, daily production reporting, blast hole sampling, and exploration sample analysis. Dust control is addressed via dust collectors at each crushing stage, while the camp facilities offer accommodation for senior management and visitors, plus food preparation and worker amenities with septic systems. Instrument and process air supply is included for the CIC plant and control systems. The project’s sustainability and economic impact are underscored by its phased pad construction strategy, which defers capital while maintaining operational flexibility. The design accounts for a 60% utilization in the crushing circuit (allowing maintenance downtime) and 92% utilization in leaching and carbon adsorption. Key ore characteristics—specific gravity 2.65 g/cm³, bulk density 1.65 t/m³, moisture 2.0%, work index 16.0 kWh/t, and abrasion index 0.75 g—informed equipment selection. Water balance modeling (Figure 17.3) ensures effective management of solution inventory. The project is being advanced as a PEA, with additional metallurgical testing recommended to optimize crushing circuit design and cyanide consumption. The process design reflects a conservative 2% discount on gold recovery from lab column tests to account for field leaching inefficiencies and pad stacking effects, and a similar discount on cyanide consumption from 0.55 kg/t to 0.20 kg/t for operating costs. Looking ahead, the Cerro Caliche gold heap leach operation is positioned to become a significant low-cost producer in Sonora, leveraging established infrastructure, a skilled local workforce (via Fimsa for crusher packages), and a favorable regulatory environment. The combination of three-stage crushing, heap leaching, and carbon-in-column adsorption offers a technically sound, capital-efficient recovery method for this bulk-tonnage gold-silver deposit.

Key Processes: Heap Leaching, Cyanidation, Gravity Separation, Crushing

Target Commodities: Gold, Silver